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Boston Faces 'Most Complex Crime Scene' In Its History

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AP Photo / Elise Amendola

No arrests have been made, no suspects have been named, and officials did not disclose any possible motive for the attack.

"This remains a very active investigation," Richard DesLauriers, special agent in charge of the FBI's Boston Division, told reporters.

DesLauriers said the investigation was taking place at various locations throughout the Boston and greater Eastern Massachusetts area, with authorities interviewing various witnesses and following up on a "variety" of leads. Officials have received "voluminous tips" from the public since the incident, DesLauriers said.

Gene Marquez, special agent in charge for the Bureau of Alcohol, Tobacco, Firearms and Explosives' Boston division, said his agency had approximately 30 forensic specialists at and around the crime scene. He urged anyone with photographic of video evidence of the attack or the surrounding area to contact the FBI's hotline.

Boston Police Commissioner Ed Davis told reporters that no one is in custody in connection with the attack.

"We are in the process of securing and processing the most complex crime scene that we have dealt with in the history of our department," Davis said.